Stress is when a physiological response is elicited from external stimuli. The stimuli can be both psychological and physiological, and stress can be long-term or short-term. Despite the way we speak about it, stress is not simply a feeling; it can actually affect a person’s biological and psychological state. When we think of stress, we tend to think of it as being equivalent to worry, but stress is much more than that, and it does not always have to be bad. There are actually two types of stress: distress and eustress, which occur from negative and positive events, respectively.

DISTRESS: Stress that occurs from negative events. For example, the stress that occurs from experiencing the death of a loved one, getting hurt, or losing a job.

EUSTRESS: Stress that occurs from positive events. For example, the stress that occurs when watching a scary movie, going on a roller coaster, or getting a job promotion.

THE FIGHT OR FLIGHT RESPONSE :

In the 1920s, American physiologist Walter Cannon described a theory about how animals handle stress based on behavior. He called this theory the fight or flight response, otherwise known as acute stress.

According to Cannon, when an animal is under intense stress (even if the stress is not real), a psychological and physiological reaction is triggered. There will be a sudden release of chemicals including adrenaline, norepinephrine, and cortisol in the body. This will create an increase in heart rate, an increase in breathing, a tightening of the muscles, and a constricting of blood vessels, resulting in the energy necessary to react by either fighting or fleeing. This involuntary response is regulated by three bodily systems: the immune system, the endocrine system, and the central nervous system.

HANS SELYE’S EXPERIMENTS WITH RATS :

The effect that stress can have on the body was first described by Hungarian scientist Hans Selye, in 1936. Selye theorized that chronic stress creates long-term chemical changes in the body, and therefore, stress could be a prominent cause of diseases.
Selye had actually stumbled upon this conclusion while working with rats as an assistant at McGill University’s biochemistry department. He had been working on an experiment that involved injecting rats with ovarian extract, hoping to discover a reaction that would lead to a new type of sex hormone.
The rats did react: their spleens, thymuses, lymph nodes, and adrenal cortexes enlarged, and they had deep bleeding ulcers in their duodenums and stomach linings. As Selye adjusted the amount of extract, these reactions would increase and decrease accordingly. Hans Selye was under the impression that he had discovered a new hormone. However, he then tried the experiment with placental extract and pituitary extract. To his surprise, the rats had the exact same responses. Still under the impression that this was a new hormone he was dealing with, Selye then tried the experiment once more with the extracts of several organs, including the kidney and spleen. The same reactions occurred every single time. Confused by these results, Selye tried one last thing: he injected a type of formaldehyde into the rats. This too brought about the same results.

HANS SELYE’S GENERAL ADAPTATION SYNDROME :

Considering his experiments with the rats to be a failure (because, after all, no new hormone was discovered), Hans Selye began looking into other possible causes for the symptoms he had discovered. A few years later, he recalled an experience he had had while studying as a young medical student in Prague. Patients would come in complaining of intestinal issues, as well as general aches and pains. Upon further examination, the patients would also end up having a fever, an enlarged liver or spleen, a skin rash, and inflamed tonsils. It wasn’t until later on that diagnosable symptoms related to particular illnesses began to appear.
Selye also became intrigued by the notion that doctors always ordered patients to perform certain treatments no matter what they were suffering from—treatments including rest, eating easily digestible food, and avoiding rooms that varied in temperature.
From his lab work with the rats and his memories of medical school, Hans Selye identified what he referred to as the general adaptation syndrome, which describes the body’s reactions to stress. According to Selye, the general adaptation syndrome can be broken down into three stages:

Alarm Reaction: This is when homeostasis is disturbed by a stressor or external stimulus and the body first notices this stimulus. It is in this first stage that Cannon’s fight or flight response comes into effect and hormones are released to provide the individual with enough energy to handle the situation at hand.
      If the energy that is released from the fight or flight response continually remains unused through a lack of physical activity, it can actually have harmful effects on the body. Too much of the hormone cortisol, for example, can damage muscle tissue and cells, and can even lead to gastric ulcers, high blood sugar levels, and stroke. If there is too much adrenaline in the body, blood vessels of the brain and heart can be damaged, and this will increase the risk of suffering from a stroke or heart attack.

Adaptation: This is when the body begins to counteract the external stimulus and restore homeostasis through recovery, renewal, and repair. This process is known as resistance, and it occurs almost immediately after the beginning of the alarm phase, and will continue until the stressful condition desists. Should a stressful condition continue, the body will remain in its state of arousal.
       A person will begin to face problems when this process begins repeating too frequently, leaving little to no time for recovery to set in. If this occurs, the individual will move into the next stage.

Exhaustion: This is when the body has been depleted of the energy, both physical and psychological, required to fight off the stressor. This is particularly true for chronic stressors, because when fighting short-term stress, a person may not be entirely depleted of his or her energy. With the energy lost, the individual can no longer resist the stressor.

As a result, stress levels go up and remain high. The individual may experience adrenal fatigue, burnout, maladaptation, overload, or dysfunction. The result of chronic stress on the body and mind is also quite striking. Nerve cells of organs and tissues can become damaged, memory and thinking can become impaired, and a person will be more likely to have anxiety or depression. High levels of stress can also contribute to rheumatoid arthritis, high blood pressure, and heart disease.